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4 25 April 2008 <br /> Mr. Jeff Baker <br /> Stockton Terminals Technicalenmittee <br /> 2. Regional Water Board staff have prepared the Waste Discharge Requirements (WDRs) <br /> required to implement the Pilot Study. A successful deployment of the Pilot Study would <br /> indicate that an enhanced bioremediation program will be an effective method of mitigating <br /> petroleum hydrocarbon migration past the A and B zone OS system. The WDRs were <br /> adopted as an uncontested item during the 25 April 2008 Regional Water Board meeting and <br /> will be sent to the STTC during the week of 28 April. By 16 May 2008, please submit an <br /> implementation schedule for conducting the Pilot Study. <br /> 3. Regional Water Board staff concur with the STTC's recommendation for installing a D-zone <br /> monitoring well between OW-8D and OW-91D. By 16 May 2008, submit a work plan to install <br /> C and D zone wells in the vicinity of A-zone monitoring well PS/MW-20 to delineate the <br /> vertical extent, and elucidate the source of petroleum hydrocarbons observed in downgradient <br /> wells OW-8C and OW-4C. <br /> 4. The Response did not address the unprecedented one to two magnitude concentration <br /> increases observed in ozone injection monitoring program well AR/MW-18B. This well is <br /> about 400 feet downgradient of the east OS system array. Some COCs observed in this well <br /> were previously non-detect (ND). The detections indicate that COCs have breached the east <br /> OS system. In accordance with the ozone injection monitoring program, the contingency plan <br /> must be activated if three or more consecutive detections of similar concentration magnitudes <br /> occur. Therefore, future concentration trends for this well must be monitored closely to assess <br /> whether additional remedial measures will required if similar concentrations continue to be <br /> present through the second quarter of 2008. <br /> 5. Regional Water Board staff could not find documentation of the contingency plan. STTC must <br /> include a brief description and/or reference to the complete contingency plan in all future <br /> QMRS to ensure adequate disclosure. STTC also needs to submit a copy of the contingency <br /> plan. <br /> 6. We concur with the STTC's proposal to conduct quarterly sampling in wells PS/P-26 and <br /> PS/MW-1 M (groundwater sampling is not currently conducted in these wells), and annual <br /> sampling in PS/P-26, TS-1, and TSM-1 for ethanol and methanol. Increases in monitoring <br /> frequency and analysis do not require MRP revisions. Please provide your recommendations <br /> for the duration of the proposed monitoring in the second or third QMR. <br /> 7. The Annual Report does not specify which monitoring wells will be monitored to track the <br /> increasing concentration trends observed in selected C and D zone wells. Please clarify which <br /> wells the STTC intends to monitor to accomplish this task in the second or third 2008 QMR. <br /> If you have any questions regarding this letter, you may contact me at (916) 464-4811 or by <br /> email at betaylor@water ards.ca.gov. <br /> BRIAN TA G. <br /> Engineering G logist <br /> cc list on next page <br />